This invention relates generally to the reduction of CO2. Sustainable production of C-based fuel requires using renewable energy to power the reductive fixation of CO2. Coupling renewable electricity to an electrolytic device is an attractive strategy for this goal because it enables the use of multiple renewable energy sources and independent optimization of catalysis. Solid oxide electrolytic cells reduce CO2 to CO efficiently at high current densities, but require operating temperatures of 750-900° C. and cannot access other products.
Materials that catalyze electrochemical CO2 reduction under mild conditions would enable the development of electrolyzers that operate at more convenient temperatures and provide access to alternative reduction products such as formic acid, alcohols and hydrocarbons. Researchers over the past three decades have identified several materials that are capable of reducing CO2 electrochemically in aqueous solutions, but none that is efficient and stable enough for practical use. In general, available electrodes suffer from one or more of three major problems: 1) a requirement for excessive reducing potentials (“overpotentials”) to reduce CO2 in preference to reducing H2O, resulting in low energetic efficiency; 2) rapid loss of CO2 reduction activity resulting from electrode poisoning; 3) production of multiple CO2 reduction products with little selectivity. There is a pressing need to discover and develop new electrochemical CO2 reduction catalysts in order for sustainable fuels to be a significant contributor to a renewable energy economy.